Thomas Hellström
8b91cdd4f8
drm/i915: Use __GFP_KSWAPD_RECLAIM in the capture code ...
The capture code is typically run entirely in the fence signalling
critical path. We're about to add lockdep annotation in an upcoming patch
which reveals a lockdep splat similar to the below one.
Fix the associated potential deadlocks using __GFP_KSWAPD_RECLAIM
(which is the same as GFP_WAIT, but open-coded for clarity) rather than
GFP_KERNEL for memory allocation in the capture path. This has the
potential drawback that capture might fail in situations with memory
pressure.
[ 234.842048] WARNING: possible circular locking dependency detected
[ 234.842050] 5.15.0-rc7+ #20 Tainted: G U W
[ 234.842052] ------------------------------------------------------
[ 234.842054] gem_exec_captur/1180 is trying to acquire lock:
[ 234.842056] ffffffffa3e51c00 (fs_reclaim){+.+.}-{0:0}, at: __kmalloc+0x4d/0x330
[ 234.842063]
but task is already holding lock:
[ 234.842064] ffffffffa3f57620 (dma_fence_map){++++}-{0:0}, at: i915_vma_snapshot_resource_pin+0x27/0x30 [i915]
[ 234.842138]
which lock already depends on the new lock.
[ 234.842140]
the existing dependency chain (in reverse order) is:
[ 234.842142]
-> #2 (dma_fence_map){++++}-{0:0}:
[ 234.842145] __dma_fence_might_wait+0x41/0xa0
[ 234.842149] dma_resv_lockdep+0x1dc/0x28f
[ 234.842151] do_one_initcall+0x58/0x2d0
[ 234.842154] kernel_init_freeable+0x273/0x2bf
[ 234.842157] kernel_init+0x16/0x120
[ 234.842160] ret_from_fork+0x1f/0x30
[ 234.842163]
-> #1 (mmu_notifier_invalidate_range_start){+.+.}-{0:0}:
[ 234.842166] fs_reclaim_acquire+0x6d/0xd0
[ 234.842168] __kmalloc_node+0x51/0x3a0
[ 234.842171] alloc_cpumask_var_node+0x1b/0x30
[ 234.842174] native_smp_prepare_cpus+0xc7/0x292
[ 234.842177] kernel_init_freeable+0x160/0x2bf
[ 234.842179] kernel_init+0x16/0x120
[ 234.842181] ret_from_fork+0x1f/0x30
[ 234.842184]
-> #0 (fs_reclaim){+.+.}-{0:0}:
[ 234.842186] __lock_acquire+0x1161/0x1dc0
[ 234.842189] lock_acquire+0xb5/0x2b0
[ 234.842192] fs_reclaim_acquire+0xa1/0xd0
[ 234.842193] __kmalloc+0x4d/0x330
[ 234.842196] i915_vma_coredump_create+0x78/0x5b0 [i915]
[ 234.842253] intel_engine_coredump_add_vma+0x36/0xe0 [i915]
[ 234.842307] __i915_gpu_coredump+0x290/0x5e0 [i915]
[ 234.842365] i915_capture_error_state+0x57/0xa0 [i915]
[ 234.842415] intel_gt_handle_error+0x348/0x3e0 [i915]
[ 234.842462] intel_gt_debugfs_reset_store+0x3c/0x90 [i915]
[ 234.842504] simple_attr_write+0xc1/0xe0
[ 234.842507] full_proxy_write+0x53/0x80
[ 234.842509] vfs_write+0xbc/0x350
[ 234.842513] ksys_write+0x58/0xd0
[ 234.842514] do_syscall_64+0x38/0x90
[ 234.842516] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 234.842519]
other info that might help us debug this:
[ 234.842521] Chain exists of:
fs_reclaim --> mmu_notifier_invalidate_range_start --> dma_fence_map
[ 234.842526] Possible unsafe locking scenario:
[ 234.842528] CPU0 CPU1
[ 234.842529] ---- ----
[ 234.842531] lock(dma_fence_map);
[ 234.842532] lock(mmu_notifier_invalidate_range_start);
[ 234.842535] lock(dma_fence_map);
[ 234.842537] lock(fs_reclaim);
[ 234.842539]
*** DEADLOCK ***
[ 234.842540] 4 locks held by gem_exec_captur/1180:
[ 234.842543] #0 : ffff9007812d9460 (sb_writers#17){.+.+}-{0:0}, at: ksys_write+0x58/0xd0
[ 234.842547] #1 : ffff900781d9ecb8 (&attr->mutex){+.+.}-{3:3}, at: simple_attr_write+0x3a/0xe0
[ 234.842552] #2 : ffffffffc11913a8 (capture_mutex){+.+.}-{3:3}, at: i915_capture_error_state+0x1a/0xa0 [i915]
[ 234.842602] #3 : ffffffffa3f57620 (dma_fence_map){++++}-{0:0}, at: i915_vma_snapshot_resource_pin+0x27/0x30 [i915]
[ 234.842656]
stack backtrace:
[ 234.842658] CPU: 0 PID: 1180 Comm: gem_exec_captur Tainted: G U W 5.15.0-rc7+ #20
[ 234.842661] Hardware name: ASUS System Product Name/PRIME B560M-A AC, BIOS 0403 01/26/2021
[ 234.842664] Call Trace:
[ 234.842666] dump_stack_lvl+0x57/0x72
[ 234.842669] check_noncircular+0xde/0x100
[ 234.842672] ? __lock_acquire+0x3bf/0x1dc0
[ 234.842675] __lock_acquire+0x1161/0x1dc0
[ 234.842678] lock_acquire+0xb5/0x2b0
[ 234.842680] ? __kmalloc+0x4d/0x330
[ 234.842683] ? finish_task_switch.isra.0+0xf2/0x360
[ 234.842686] ? i915_vma_coredump_create+0x78/0x5b0 [i915]
[ 234.842734] fs_reclaim_acquire+0xa1/0xd0
[ 234.842737] ? __kmalloc+0x4d/0x330
[ 234.842739] __kmalloc+0x4d/0x330
[ 234.842742] i915_vma_coredump_create+0x78/0x5b0 [i915]
[ 234.842793] ? capture_vma+0xbe/0x110 [i915]
[ 234.842844] intel_engine_coredump_add_vma+0x36/0xe0 [i915]
[ 234.842892] __i915_gpu_coredump+0x290/0x5e0 [i915]
[ 234.842939] i915_capture_error_state+0x57/0xa0 [i915]
[ 234.842985] intel_gt_handle_error+0x348/0x3e0 [i915]
[ 234.843032] ? __mutex_lock+0x81/0x830
[ 234.843035] ? simple_attr_write+0x3a/0xe0
[ 234.843038] ? __lock_acquire+0x3bf/0x1dc0
[ 234.843041] intel_gt_debugfs_reset_store+0x3c/0x90 [i915]
[ 234.843083] ? _copy_from_user+0x45/0x80
[ 234.843086] simple_attr_write+0xc1/0xe0
[ 234.843089] full_proxy_write+0x53/0x80
[ 234.843091] vfs_write+0xbc/0x350
[ 234.843094] ksys_write+0x58/0xd0
[ 234.843096] do_syscall_64+0x38/0x90
[ 234.843098] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 234.843101] RIP: 0033:0x7fa467480877
[ 234.843103] Code: 75 05 48 83 c4 58 c3 e8 37 4e ff ff 0f 1f 80 00 00 00 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24
[ 234.843108] RSP: 002b:00007ffd14d79b08 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[ 234.843112] RAX: ffffffffffffffda RBX: 00007ffd14d79b60 RCX: 00007fa467480877
[ 234.843114] RDX: 0000000000000014 RSI: 00007ffd14d79b60 RDI: 0000000000000007
[ 234.843116] RBP: 0000000000000007 R08: 0000000000000000 R09: 00007ffd14d79ab0
[ 234.843119] R10: ffffffffffffffff R11: 0000000000000246 R12: 0000000000000014
[ 234.843121] R13: 0000000000000000 R14: 00007ffd14d79b60 R15: 0000000000000005
v5:
- Use __GFP_KSWAPD_RECLAIM rather than __GFP_NOWAIT for clarity.
(Daniel Vetter)
v6:
- Include an instance in execlists_capture_work().
- Rework the commit message due to patch reordering.
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Ramalingam C <ramalingam.c@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211108174547.979714-3-thomas.hellstrom@linux.intel.com
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8b91cdd4f8